! IMPORTANT NOTE
! These weight need to be multiplied by 1/2
        gx( 0) = 0.5_num + cell_frac_x
        gx( 1) = 0.5_num - cell_frac_x

        gy( 0) = 0.5_num + cell_frac_y
        gy( 1) = 0.5_num - cell_frac_y

        gz( 0) = 0.5_num + cell_frac_z
        gz( 1) = 0.5_num - cell_frac_z
